Telephone



NI'TED STATEs ATENT FFICE.

STEPHEN F. SHERMAN, OF NEl/V YORK, ASSIGNOR OF ONE-HALF TO GEORGE F.SHAVER, OF YONKERS, NEWV YORK.

TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 476,026, dated May 31,1892. Application filed March 2,1892- Serial No. 423,494. (No model.)

To all whom it may concern:

Be it known that I, STEPHEN F. SHERMAN, a citizen of the United Statesof America, residing in the city, county, and State of New York, haveinvented certain new and useful Improvements in Telephones, of which thefollowing is a specification.

My invention is an improvement in telephones; and it consists in avariable resistto ance in the form of a conducting strip or ribbonfolded or creased to form plaits, which is in the primarytranemitter-circuit and is connected with the diaphragm of thetransmitter either directly or indirectly, whereby the plaits of thestrip are opened and closed and the resistance through the entireplaited conductor varied with the movements of the diaphragm, and incertain other details hereinafter described and claimed. Referring tothe accompanying drawings,

Figure 1 is a plan and view for the transmitter seen from the front.Fig. 2 is a side view in cr0ss-section on the line x a: of Fig.1. Fig. 3is a perspective view of the plaitedre- 2 5 sistance-strip.

A is the outer casing of the transmitter, in which the mouth-piece B andthe operative parts of the transmitter are supported.

O is the diaphragm. D is the multiplying-lever, pivoted to the casing ata and carrying on its end a conducting block (1, to Which one end of theplaited conducting-strip E is attached. This plaited conductor rests ina horizontal position upon the floor of a'protective casing F and isattached at its other end to ablock on the end of an adj Listing-screwG. This screw works in a thread in the casing A, and by turning thescrew in or out the folds of the 40 conductor E can be made as close oras open as is desired. An electric battery is shown connected with thelever D and embracing within its circuit the conductor E and the primarycoils of an induction-coil, the secondary coils of which are connectedwith the linewires.

The conducting-strip E should be of high resistance compared with theother resistance of the primary or battery circuit. It can be made inthe following way: A flexible strip or ribbon of silk, cotton, paper, orother suitable material is painted with white lead or other suitablepaint or varnish and while this coating is still moist is coated with alayer of powdered carbon. There is thus formed a" carbonized ribbonwhich is a corn ductor of electricity of high resistance, or a thinstrip of vulcanized fiber maybe used; butl do not limit myself to aribbon of any partieular composition.

The operation of the transmitter is as follows: When the diaphragm O iscaused to vibrate by sound-waves, its vibrations are transmitted throughthe lever D, by which they are considerably enlarged, to the plaitedstrip E. The folds of this strip are closed or opened, according to thedirection of motion of the diaphragm and lever. Thus the resisttance ofthe strip, and hence of the primary circuit, is varied, and the currentsare induced in the secondary coils of the induction-coil, which traversethe line-wires and operate the receiver, where the sounds which set upthe vibration of the diaphragm of the transmitter are reproduced.

The ribbon or conductingstrip should be narrow and thin, but strong, andshould be covered with the powdered carbon as evenly as possible.

Without limiting myself to the precise details shown, what I claim, anddesire to secure by Letters Patent of the United States 1s- 1. In atelephone-transmitter, the combination of a vibrating diaphragm andavariable resistance connected therewith and included in the circuit,made of a piece of conducting material creased or folded toform plaits,substantially as described.

2. In a telephone-transmitter, the combination of a vibrating diaphragmand a variable resistance connected therewith and included in thecircuit, made of a piece of carbon creased or folded to form plaits,substantially as described. 5

Subscribed by me, in New York city, this 29th day of February, 1892.

STEPHEN F. SHERMAN.

In presence of- THOMAS EWING, J r., M. W. CoPPoRTo.

